Genetic factors associated with elevation of uric acid after treatment with thiazide-like diuretic in patients with essential hypertension.

We investigated changes in blood pressure (BP) and metabolic adverse effects, especially elevation of uric acid (UA), after treatment with a thiazide-like diuretic (TD) in patients with essential hypertension. Furthermore, the role of genetic factors in the elevation of UA by TD was assessed by a 500 K SNP DNA microarray. The subjects included 126 hypertensive patients (57 women and 69 men, mean age 59 ± 12 years) who registered for the GEANE (Gene Evaluation for ANtihypertensive Effects) study. After one month of the nontreatment period, TD, indapamide, angiotensin II receptor antagonist valsartan, and Ca channel blocker amlodipine were administered to all patients for 3 months each in a randomized crossover manner. BP, renal function, serum UA level, and electrolytes were measured at baseline and at the end of each treatment period. Single nucleotide polymorphisms (SNPs) associated with UA elevation after treatment with indapamide were investigated by a genome-wide association study (GWAS). Indapamide significantly decreased both office and home BP levels. Treatment with indapamide also significantly reduced the estimated glomerular filtration rate and serum potassium and increased serum UA. Patients whose UA level increased more than 1 mg/dl showed significantly higher baseline office SBP and plasma glucose and showed greater decline in renal function compared with those who showed less UA increase (<1 mg/dl). Some SNPs strongly associated with an increase in UA after treatment with indapamide were identified. This study is the first report on SNPs associated with UA elevation after TD treatment. This information may be useful for the prevention of adverse effects after treatment with TD.

Association of genetic variants for susceptibility to obesity with type 2 diabetes in Japanese individuals.

AIMS/HYPOTHESIS: In populations of East Asian descent, we performed a replication study of loci previously identified in populations of European descent as being associated with obesity measures such as BMI and type 2 diabetes. METHODS: We genotyped 14 single nucleotide polymorphisms (SNPs) from 13 candidate loci that had previously been identified by genome-wide association meta-analyses for obesity measures in Europeans. Genotyping was done in 18,264 participants from two general Japanese populations. For SNPs showing an obesity association in Japanese individuals, we further examined diabetes associations in up to 6,781 cases and 7,307 controls from a subset of the original, as well as from additional populations. RESULTS: Significant obesity associations (p < 0.1 two-tailed, concordant direction with previous reports) were replicated for 11 SNPs from the following ten loci in Japanese participants: SEC16B, TMEM18, GNPDA2, BDNF, MTCH2, BCDIN3D-FAIM2, SH2B1-ATP2A1, FTO, MC4R and KCTD15. The strongest effect was observed at TMEM18 rs4854344 (p = 7.1 × 10(-7) for BMI). Among the 11 SNPs showing significant obesity association, six were also associated with diabetes (OR 1.05-1.17; p = 0.04-2.4 × 10(-7)) after adjustment for BMI in the Japanese. When meta-analysed with data from the previous reports, the BMI-adjusted diabetes association was found to be highly significant for the FTO locus in East Asians (OR 1.13; 95% CI 1.09-1.18; p = 7.8 × 10(-10)) with substantial inter-ethnic heterogeneity (p = 0.003). CONCLUSIONS/INTERPRETATION: We confirmed that ten candidate loci are associated with obesity measures in the general Japanese populations. Six (of ten) loci exert diabetogenic effects in the Japanese, although relatively modest in size, and independently of increased adiposity.

Evaluation of the antiobesity effects of an amino acid mixture and conjugated linoleic acid on exercising healthy overweight humans: a randomized, double-blind, placebo-controlled trial.

This single-centre, randomized, double-blind, placebo-controlled trial investigated the effects of administering a mixture of four amino acids (lysine, proline, alanine and arginine) with or without conjugated linoleic acid to healthy overweight humans before and after exercising. Forty-one healthy subjects (body mass index >or= 23 to < 30 kg/m(2)) completed the study following randomization to receive either placebo or one of three test supplements: amino acid mixture 0.76 g/day; amino acid mixture 1.52 g/day; or amino acid mixture 1.52 g/day coadministered with conjugated linoleic acid 1.6 g/day. Each of the study treatments was administered 30 min before and immediately after a period of daily exercise, which was delivered by an exercise expert, for a period of 12 weeks. When compared with the placebo group, several indicators, such as waist and hip circumferences, were found to have significantly decreased in the test supplement groups compared with the placebo. These results suggest that ingestion of these supplements might enhance the fat-burning effects of exercise.

Common variants at the GCK, GCKR, G6PC2-ABCB11 and MTNR1B loci are associated with fasting glucose in two Asian populations.

AIMS/HYPOTHESIS: To test fasting glucose association at four loci recently identified or verified by genome-wide association (GWA) studies of European populations, we performed a replication study in two Asian populations. METHODS: We genotyped five common variants previously reported in Europeans: rs1799884 (GCK), rs780094 (GCKR), rs560887 (G6PC2-ABCB11) and both rs1387153 and rs10830963 (MTNR1B) in the general Japanese (n = 4,813) and Sri Lankan (n = 2,319) populations. To identify novel variants, we further examined genetic associations near each locus by using GWA scan data on 776 non-diabetic Japanese samples. RESULTS: Fasting glucose association was replicated for the five single nucleotide polymorphisms (SNPs) at p < 0.05 (one-tailed test) in South Asians (Sri Lankan) as well as in East Asians (Japanese). In fine-mapping by GWA scan data, we identified in the G6PC2-ABCB11 region a novel SNP, rs3755157, with significant association in Japanese (p = 2.6 x 10(-8)) and Sri Lankan (p = 0.001) populations. The strength of association was more prominent at rs3755157 than that of the original SNP rs560887, with allelic heterogeneity detected between the SNPs. On analysing the cumulative effect of associated SNPs, we found the per-allele gradients (beta = 0.055 and 0.069 mmol/l in Japanese and Sri Lankans, respectively) to be almost equivalent to those reported in Europeans. CONCLUSIONS/INTERPRETATION: Fasting glucose association at four tested loci was proven to be replicable across ethnic groups. Despite this overall consistency, ethnic diversity in the pattern and strength of linkage disequilibrium certainly exists and can help to appreciably reduce potential causal variants after GWA studies.

Hypertension in a patient with Gitelman's syndrome.

Gitelman's syndrome is an autosomal recessive disorder characterized by sodium wasting and hypotension. A middle-aged woman was diagnosed with Gitelman's syndrome because of typical clinical manifestations in the youth and homozygous mutations of 18-base-pair insertion in exon 6 of thiazide-sensitive NaCl-cotransporter gene. It was unusual that she showed hypertension with advancing age. Her serum potassium levels remained low at around 3.5 mEq/l despite potassium supplementation. This case demonstrates that hypertension could result in spite of the extremely decreased sodium reabsorption in Gitelman's syndrome and that essential hypertension is genetically heterogeneous, and abnormality of all genes may not be necessarily required to cause blood pressure rise.

Endothelin-1 gene variant associates with blood pressure in obese Japanese subjects: the Ohasama Study.

A recent report based on the results of 2 epidemiological studies, the Etude Cas-Temoin de l'Infarctus Myocarde (ECTIM) and the Glasgow Heart Scan Study, revealed that a G/T polymorphism with an amino acid substitution (Lys-->Asn) at codon 198 in exon 5 of the endothelin-1 gene (ET-1) is associated with blood pressure in overweight people. They suggested that G/T polymorphism of ET-1 strongly interacted with body mass index (BMI) in the determination of BP levels. To examine interaction among G/T polymorphism of ET-1, BMI, and BP, we performed an association study in a general Japanese population. Subjects (n=1250) were recruited from Ohasama, a cohort in a rural community of northern Japan. DNA was extracted from buffy coat of participants, and G/T polymorphism of ET-1 was determined by the TaqMan probe polymerase chain reaction method, a powerful tool for semiautomatic genotype determination of a large number of samples. Frequency of T (Asn 198) allele in Japanese (27%) was slightly but significantly higher than in whites (24%). Baseline characteristics (age, BMI, systolic and diastolic BP, and antihypertensive treatment) of all subjects were not significantly different according to the genotype of G/T polymorphism. However, in obese subjects (> or =25 kg/m(2)) diastolic BPs were significantly associated with G/T polymorphism of ET-1. After adjustment for confounding factors, significant association remained; for overweight subjects, diastolic BP level in those with T allele (GT + TT) was 1.8 mm Hg (P=0.04) higher than in those with GG genotype. That similar results were obtained from subjects of different races suggests that the Lys198Asn polymorphism of ET-1 is involved in determination of BP levels in obese subjects.

Aldosterone synthase gene (CYP11B2) C-334T polymorphism, ambulatory blood pressure and nocturnal decline in blood pressure in the general Japanese population: the Ohasama Study.

OBJECTIVE: The C-344T polymorphism in the 5'-flanking region of the aldosterone synthase (CYP11B2) gene has been suggested to be associated with hypertension and disturbed circadian blood pressure (BP) rhythm through its effect on aldosterone synthesis. However, previous findings on this topic have been inconsistent. DESIGN: A cross-sectional study. SUBJECTS AND METHODS: We investigated the CYP11B2 C-344T genotype in 802 subjects, aged 40 and over, in a Japanese community, who gave written informed consent and were monitored for 24 h ambulatory BP. RESULTS: The frequencies of the CC, CT, and TT genotypes in these Japanese subjects were 0.14, 0.44, and 0.42, showing a higher frequency of the T allele (0.64) than in Caucasians. Although there was no significant difference in 24 h ambulatory BP levels among the genotypes, the nocturnal decline in BP was significantly greater in the CC homozygous subjects than in other subjects (P = 0.0065 for systolic and P = 0.031 for diastolic decline in nocturnal BP). Detailed analyses demonstrated that this association was significant only in aged (60 years and over) or male subjects. The prevalence of previous cardiovascular disease was significantly less in these subjects with the CC genotype than in those with the TC and TT genotypes, although age, body mass index, male gender, smoking, use of alcohol and antihypertensive medication did not differ among the three genotypes. There was no significant difference among the three genotypes in biochemical and hormonal parameters. CONCLUSION: Although the C-344 T polymorphism of CYP11B2 did not directly influence the level of 24 h BP, the CC genotype was associated with decreased nocturnal BP in elderly or male Japanese. Since prevalence of previous cardiovascular disease was significantly less in homozygous CC subjects, greater nocturnal BP decline in this genotype appears to be beneficial in the circadian BP rhythm.

Association analyses between genetic polymorphisms of endothelial nitric oxide synthase gene and hypertension in Japanese: The Suita Study.

OBJECTIVES: Endothelium-derived nitric oxide plays a key role in the regulation of vascular tone. Recently, endothelial nitric oxide synthase (eNOS) gene polymorphisms were reported to be associated with hypertension or coronary spasm. We investigated the association between the eNOS gene polymorphisms and hypertension in a large population-based sample of 4055 Japanese. DESIGN AND METHODS: We investigated two polymorphisms of the eNOS gene, Glu298Asp polymorphism of exon 7 and T(-786)C polymorphism of the promoter region. The genotype distribution in hypertensive subjects was compared to that in the other subjects. The influence of the genotype on blood pressure values was analyzed in the subjects not taking hypertensive medication. The promoter activities of the eNOS gene with the (-786)T or (-786)C allele were measured by a luciferase reporter gene assay. RESULTS: There was significant linkage disequilibrium between the two polymorphisms (P < 0.0001). The genotype distribution of the Glu298Asp or T(-786)C polymorphism did not differ between the hypertensive and the other subjects. No significant differences in the blood pressure of subjects not taking hypertensive medication were observed among the three genotypes of Glu298Asp or T(-786)C polymorphisms. No significant differences in the promoter activity were observed between bovine endothelial cells transfected with the (-786)T and (-786)C alleles. CONCLUSIONS: Our data suggested that these polymorphisms of the eNOS gene are unlikely to be major factors in the susceptibility to hypertension in the Japanese population studied.

The aldehyde dehydrogenase 2 gene is a risk factor for hypertension in Japanese but does not alter the sensitivity to pressor effects of alcohol: the Suita study.

Excessive alcohol consumption is a potent risk factor for high blood pressure. About half of Japanese show an extremely high sensitivity to alcohol, which is due to a genetic deficiency in an isoenzyme of aldehydede-hydrogenase with a low Km (ALDH2). It is possible that the effects of alcohol consumption on blood pressure differ according to the ALDH2 genotype. The purpose of the present study was to assess the influence of the ALDH2 genotype on the pressor effects of alcohol. The influence of the ALDH2 genotype on blood pressure was investigated in a large cohort (4,000 subjects) representing the general population in Japan. The genotype was determined by the TaqMan method. The genotype was significantly associated with alcohol consumption, gamma-GTP level, and HDL cholesterol level in both males and females. The odds ratio for the presence of hypertension for the Glu/Glu genotype in comparison to other genotypes was 1.67 (p< 0.0001, odds ratio=1.37-2.08, 95% confidence interval) among males. In contrast, the ALDH2 genotype had no significant effects on blood pressure among females. To investigate whether the ALDH2 genotype affected the sensitivity to the pressor effects of alcohol, we analyzed the effects of the ALDH2 genotype (Lys/Lys+Lys/Glu=0, Glu/Glu=1) and the level of alcohol consumption on blood pressure values after adjusting for age and BMI (residuals after adjusting for age and BMI). Among males, while the level of alcohol consumption significantly affected systolic, diastolic and pulse pressure, no significant interaction was observed between the ALDH2 genotype and the level of alcohol consumption in determining blood pressure levels. These results suggest that the Glu/Glu genotype is a potent risk factor for hypertension among males mainly through its association with the level of alcohol consumption, and that the ALDH2 genotype does not affect the sensitivity to the pressor effects of alcohol.

Effects of antihypertensive drugs and gene variants in the renin-angiotensin system.

Many genes and environmental factors are involved in the pathogenesis of hypertension, but the exact cause of essential hypertension has not yet been clarified. Gene polymorphism of the renin-angiotensin system (RAS) is one of the candidates. In the current study, we examined whether there was a correlation between the gene polymorphisms in RAS and either the choice of antihypertensive drugs or their efficacy. Subjects with essential hypertension (n=299) were recruited from among the outpatients of Osaka University Hospital and provided their informed consent for genetic analysis. Physicians freely chose the antihypertensive drugs and adjusted its dose until the patient's blood pressure was well controlled. The efficacy of each antihypertensive drug was estimated using the following formula: ABP=BP 1 (before treatment) - BP 2 (after treatment)/BP 1 x 100 (%). Gene variants in RAS were determined using PCR or PCR-RFLP (restriction fragment of polymorphism). The gene polymorphisms of RAS were not associated with delta SBP or ADBP. However, the mean ASBP in subjects with a deletion homozygote of the angiotensin converting enzyme gene (ACE/DD) was significantly lower (p<0.05) than that in patients with an insertion I allele of the ACE gene. The gene polymorphisms of RAS did not significantly affect the choice of antihypertensive drugs. Even though gene polymorphism in the renin angiotensin system was not a major factor in the antihypertensive therapy, the determination of genotype might be of help in the management of essential hypertension.

Association of sodium channel gamma-subunit promoter variant with blood pressure.

The SCNN1G gene, located on human chromosome 16p12, encodes the gamma subunit of the amiloride-sensitive epithelial sodium channel, and mutations in SCNN1G can result in Liddle's syndrome or pseudohypoaldosteronism type I. We identified sequence variations in the promoter region of SCNN1G and examined the association between this polymorphism and blood pressure in a large cohort (n=4075) representing the general population in Japan. We found T(-1290)C, T(-501)G, G(-173)A, and G(-104)T polymorphisms in the promoter region of SCNN1G and confirmed the existence of T387C and T474C polymorphisms in exon 3 and the C1947G polymorphism in exon 13. Because the genotypes of the T(-1290)C, T(-501)G, G(-104)T, and T474C polymorphisms were in tight linkage disequilibrium, we selected the T474C and G(-173)A polymorphisms for an association study. The G(-173)A polymorphism of SCNN1G had a significant effect on systolic pressure (P=0.0050) and pulse pressure (P=0.0050). The AA genotype was associated with an 11 mm Hg drop in systolic pressure and an 8 mm Hg drop in pulse pressure and with a higher prevalence of hypotension (P=0.0195). A transient transfection assay using MDCK cells and human renal epithelial cells indicated that the promoter activity of the G(-173) allele was higher than that of the A(-173) allele. Although the effects of the A(-173) allele were recessive and although the AA genotype was found in just 0.7% of our study population, we observed that this variation of human SCNN1G had significant effects on blood pressure.

Lack of correlation between Mbo I restriction fragment length polymorphism of renin gene and essential hypertension in Japanese.

Predisposition to essential hypertension is associated with gene polymorphisms of the renin angiotensin system (RAS). Gene polymorphisms of the angiotensinogen and angiotensin converting enzyme genes are known to be risk factors for hypertension, while few studies concerning the renin gene polymorphism have been published. In the present investigation, we carried out a case control study using a Japanese population to examine the genetic influence of the renin gene on the predisposition to hypertension. Patients (n=235) recruited from outpatients at Osaka University Hospital and diagnosed with essential hypertension or receiving long-term antihypertensive medication participated in the study. Normotensive control subjects (n=510) without a history of hypertension and without diabetes mellitus were recruited from the same population, and were sex-matched with experimental subjects. A polymorphism in intron 9 of the human renin gene was determined as the Mbo I restriction fragment length polymorphism (Mbo I-RFLP). There was no significant association between Mbo I-RFLP of the renin gene and predisposition to essential hypertension in Japanese (p>0.05, chi2=2.1). These results suggest that the Mbo I (+) allele of the renin gene does not increase the risk for hypertension in Japanese.

[Genetic polymorphisms of the renin-angiotensin system].

Essential hypertension is a multifactorial disease which is evoked by multiple environmental and genetic factors. Recent progress in molecular biology enables us a comprehensive understanding of the molecular pathogenesis of this disease. The genes of renin-angiotensin system such as renin, angiotensinogen, angiotensin-converting enzyme and angiotensin receptors genes are all reported as positive linkage to hypertension. Now ongoing progress of the human genome project will further accelerate the molecular studies on the rennin-angiotensin system and hypertension.

Low potentiality of angiotensin-converting enzyme gene insertion/deletion polymorphism as a useful predictive marker for carotid atherogenesis in a large general population of a Japanese city: the Suita study.

BACKGROUND AND PURPOSE: Some previous studies, almost all western, have investigated whether there is a relationship between the insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) and carotid atherosclerosis. The results, however, have not been consistently positive. Further, there have been few investigations based on a large, general population. Therefore, the present study aimed to clarify whether ACE gene deletion polymorphism was associated with carotid atherosclerosis in a large Japanese general population with a more homogeneous genetic background than Caucasian populations. METHODS: Subjects aged 30 to 86 years were randomly selected from Suita City, located in Osaka, the second largest urban area of Japan, and included 1894 men and 2137 women. With the aid of high-resolution ultrasonography, carotid atherosclerosis was evaluated using our atherosclerotic indexes of intimal-medial thickness (IMT), plaque number (PN), plaque score (PS), and percentage of stenosis of the carotid artery assessed using high-resolution B-mode ultrasonography. ACE gene I/D polymorphism was detected by polymerase chain reaction. RESULTS: There were no significant differences among the ACE genotypes for age and conventional cardiovascular risk factors, except for systolic blood pressure (SBP) and the percentage of hypertension in men. The values of IMT, PN, and PS as carotid atherosclerotic indexes were not significantly different among genotypes for either sex. After adjusting for age, body mass index, smoking habit, high-density lipoprotein cholesterol, triglycerides, presence of hypertension, presence of diabetes mellitus, and presence of hyperlipidemia, the estimated ORs for the presence of IMT >/=1.10 mm (defined as thickened IMT), according to ACE genotype (DD versus II, DD+ID versus II, and DD versus ID+II), for men were 0.80 (95% CI 0.60 to 1.23), 0.89 (0.62 to 1.29), and 0.89 (0.70 to 1.28), respectively. On the other hand, the ORs for women after the same adjustment were 0.92 (95% CI 0.58 to 1.35), 0.93 (0.59 to 1.45), and 0.91 (0.59 to 1.27), respectively. CONCLUSIONS: Our present data suggest that ACE I/D polymorphism is not potentially a useful predictive marker for carotid atherogenesis when investigated in a large and homogeneous general Japanese population of 4031 subjects, a finding similar to that in a Caucasian population study, the Perth Carotid Ultrasound Disease Assessment Study, an Australian study based on a general population using 1111 subjects.

A common mutation of low-density lipoprotein receptor gene is associated with essential hypertension among Japanese.

Candidate genes offer one approach to the identification of the genetic susceptibility to hypertension. A common gene variant of the low-density lipoprotein (LDL) receptor gene (LDLR) that affects plasma LDL metabolism within the normolipidaemic range, may be such a candidate gene. A common mutation of LDLR, C1773T, was associated with lipid metabolism such that the T1773 allele increased plasma LDL levels in a Caucasian population. The present study examined whether C1773T/LDLR was associated with essential hypertension in a Japanese population. Subjects with essential hypertension (EHT, n = 300) with a family history of hypertension, and controls (NT, n = 310, sex- and age-matched with EHT) were recruited from among out-patients at Osaka University Hospital. A C1773T substitution at codon 570 in LDLR was determined using PCR-Hinc II-RFLP. It was revealed that the C1773 allele was significantly more frequent (0.89) among hypertensive patients (chi2 = 9.58, P < 0.01) than normotensives (0.83), the calculated odds ratio being 1.7 (95% CI: 1.2-2.4). The effect of the T1773 allele on increasing cholesterol was significant in normotensives without antihyperlipidaemic medication, but not in hypertensives. After adjustments of confounding factors, the estimated odds ratio for hypertension in the subjects with C1773 homozygote increased to 2.1 (95% CI: 1.3-3.5), suggesting that this polymorphism is an independent risk factor for hypertension. Our results show that the C1773 mutant of LDLR increases susceptibility to hypertension, but not via hypercholesterolaemia.

Lack of association between genetic polymorphism of CYP11B2 and hypertension in Japanese: the Suita Study.

Aldosterone synthase (CYP11B2) is a key enzyme in the biosynthesis of aldosterone. Recently, a polymorphism in the 5'-flanking region of the CYP11B2 gene [T(-344)C] has been reported to be associated with blood pressure and plasma aldosterone levels. We investigated the association between this polymorphism and hypertension in a large population-based sample of 4,000 Japanese. The genotype distribution in hypertensive subjects (n=1,535) was compared to that in normotensive subjects (n=2,514). In subjects not receiving antihypertensive medication, the influence of the genotype on blood pressure values adjusted for clinical covariates was analyzed. All analyses were performed separately for men and women. The genotype distribution did not differ between hypertensive and normotensive subjects in either men (frequency of C allele: 30.3% vs. 31.4%, p=0.48) or women (31.5% vs. 31.7%, p=0.93). There were no significant differences in systolic blood pressure, diastolic blood pressure, or pulse pressure among the three genotypes in either men or women who had not received hypertensive medication. Our data suggest that the T(-344)C polymorphism of CYP11B2 is unlikely to influence blood pressure status in the Japanese population.

Symposium on the etiology of hypertension--summarizing studies in 20th century. 1. Hypertension and genes.

Under classical strategy, scientists have tried first to find a physiological phenomenon specific for essential hypertension, then to identify the protein underlying the physiological abnormality, and finally to clarify the causative gene which encoded the protein. On the other hand, under the reverse genetic approach, the correlation between hypertension and genetic abnormality is identified first, and then the pathogenesis is clarified-in reverse order. Therefore, it is not extraordinary for unexpected results to be obtained in the correlation between a gene and a disease, suggesting that this approach has a possibility to be a breakthrough in the chaos of hypertension research.